This invention relates to a method of and an appartus for transferring heat to food articles and, more particularly, to a novel method of and apparatus for such purpose that are particularly adapted for holding previously-cooked food articles quite near to a preferred temperature for prolonged time periods, and which can also be employed to initially cook food articles or to complete the cooking of food articles that have been previously partially cooked.
In the past, several forms of old methods and apparatus have been provided for attempting to hold previously-cooked food articles near to a preferred temperature, which have been variously commonly referred to as "hot cabinets", "warming safes", "warming receptacles", "food heating carts", and "caterers' vehicles".
One recently quite popular form of such prior-art apparatus is marketed by Crescent Metal Products, Inc. of Cleveland, Ohio, as its Model H-138-CDD-1834 "hot cabinet", and basically comprises a vertically elongate cabinet or chamber, the exterior of the bottom of which is supported on casters for movement, and the interior of the bottom of which supports an electrically-powered blower that is located closely adjacent to an electrically-powered heater to thus circulate through the cabinet a heat-transferring medium consisting of heated air, which, in turn, passes over a plurality of horizontally-arranged, vertically spaced apart food articles supporting trays that are mounted within the cabinet above the blower and the heater. And, the access opening which extends almost the entire height of the fromt of the cabinet is provided with closure means that comprise a pair of hinged "dutch doors" for the stated purpose of minimizing the loss of the heated air from the cabinet interior while access is being obtained. Modified versions of this form of prior-art apparatus are also shown in U.S. Pat. Nos. 3,999,475 and 4,010,349, wherein means are also provided for regulating the relative humidity within the cabinet and transferring water vapor to the food articles supported therein which include sump means for containing water located adjacent to the interior of the cabinet bottom and having an opening fluid-connected to the cabinet interior.
With the just-described blower-circulated, electrically-heated air forms of prior-art apparatus, it has been most difficult to maintain food articles which are contained within the cabinet anywhere near to the preferred temperature when the cabinet access doors are opening by their users. There has also been considerable temperature variation between those food articles which have been supported in the upper and lower extremities of the cabinets of such prior-art forms of apparatus, with those supported lower in the cabinet and closer to the electric heater being kept warmer than those supported higher in the cabinet and, thus, farther away from the heater.
U.S. Pat. Nos. 377,594; 518,042; 1,223,311; 1,752,749; and 3,389,946 illustrate alternative forms of such prior-art apparatus wherein either steam or heated water, instead of heated air, is utilized for the heat-transferring medium. However, as shown and described in these last-mentioned five U.S. Patents, all of these additional prior-art forms of apparatus basically differ from the novel apparatus that is provided in accordance with the present invention, in that none of those old apparatus provides any pump means for circulating the steam of heated water that is employed as the heat-transferring medium between a reservoir in which the heat is supplied to the heat-transferring medium by heater means and radiator means by which the heat is transferred from the heat-transferring medium to the food articles that are supported within the cabinet or chamber nor any control means which are connected to the heater means for controlling to within .+-. a few .degree.F. the desired temperature to which the heat-transferring medium is to be heated and maintained by the heater means.
Instead of providing pump means, these just-noted steam and heated water forms of prior-art apparatus rely upon thermal convection to cause circulation of the heat transferring medium between their reservoir and radiator means and, in order to obtain such convective circulation, the heated water or steam must be maintained at or quite near to 212.degree. F. (the boiling point of water). And, since 212.degree. F. is usually more than 60.degree. F. higher than the preferred "holding" temperature of most food articles, these steam and heated water forms of prior-art apparatus can cause considerable undesired additional cooking or "overcooking" of cooked food articles which are held therein.
The U.S. Department of Agriculture has long determined that there is considerable danger of spoilage and salmonella (food poisoning bacteria) development in food articles which are held for even fairly short periods of time at temperatures ranging between 40.degree. F. and 140.degree. F. Quite recently, that same agency has increased this hazardous temperature limit to 145.degree. F. for beef food articles. And, with all of the aforenoted forms of prior-art apparatus, problems have been encountered in attempting to maintain warm food articles held therein at temperatures about 140.degree. F. without also causing considerable undesired additional cooking or "overcooking" of them.
The present invention is directed toward the provision of a novel method of and an apparatus for transferring heat to food articles, which are particularly adapted for holding previously-cooked food articles quite near to a preferred temperature for prolonged time periods and eliminates or greatly mitigates the aforenoted problems that have been encountered with prior-art apparatus which have been employed in an attempt to achieve that purpose, and which can also be employed to initially cook food articles or to complete the cooking of food articles that have been previously partially cooked.